In a known milking system, wherein teat cups are automatically attached to the teats of a milking animal to be milked, a robot arm with a gripper is provided to grip and hold teat cups during the attachment of the teat cups. A laser emitting laser light and a video camera provided to register laser light as reflected from the teats of the milking animal are mounted on the robot arm. By aid of a method known as laser triangulation, the positions of the teats can be calculated. The movement of the robot arm can then be controlled in response to the calculated positions to be capable of finding the teats for the teat cup attachments.
In order to operate satisfactorily, the robot arm needs to be close to the teats. Since each milking animal has a different constitution (the udders of the milking animals may be located at quite different locations) it may be difficult for the above arrangement to find the teats of a milking animal which has not been milked before, and for which consequently no teat position data is available. The milking system is thus typically teached approximately where to find the teats of the milking animal manually by the farmer. Further, the position of the milking animal in a longitudinal direction with respect to the milking animal is measured by a sensor, which senses the position of a rear plate as displaced by the back of the milking animal while standing in a milking box. The following times the same milking animal is identified in the milking box, the milking system refers to the actual position of the rear plate as measured, and to the knowledge of the milking animal's constitution, i.e. the relative location of its teats, in order to determine an approximate position of the teats of the milking animal.
Further, several approaches for automatically teaching the milking system where to approximately find the teats of the milking animal are known in the art.
U.S. Pat. No. 6,532,892 B1 discloses a method for finding the teats of a milking animal based on sequential movements of a scanning head in various directions.
U.S. Pat. No. 4,867,103 discloses a milking system comprising four robot arms, each being provided with a teat cup and detector means. A camera arrangement is fixedly arranged outside of the milking stall. Approximate positioning of the teat cups are made by controlling the four arms from information supplied by the camera arrangement. This is continued until the teats reach the field of action of the detector means associated with the different milking cups and designed to allow the final positioning thereof, the arms being then moved in response to the signals received from the detector means.